1. Field of the Invention
The present invention relates to bonding structures and semiconductor device manufacturing apparatuses. More specifically, the present invention relates to a bonding structure for bonding a connecting member to a metal terminal embedded in a ceramic member, a bonding structure including a connecting member for supplying an electric power to an electrode embedded in a ceramic member, and a semiconductor device manufacturing apparatus having this bonding structure.
2. Description of the Related Art
Semiconductor wafer susceptors such as an electrostatic chuck in which an electrode is embedded in a ceramic member are used in the field of semiconductor device manufacturing apparatuses such as an etching apparatus, a CVD apparatus or the like. Examples of the semiconductor wafer susceptors include: a semiconductor wafer susceptor in which an electrode is embedded in a base material such as aluminum nitride or dense alumina, and is configured to function as a discharge electrode for generating plasma; a semiconductor wafer susceptor which includes metal resistors (heater) embedded in a base material such as aluminum nitride or alumina, and is configured to function as a ceramic heater for controlling the temperature of a wafer in a heat treatment processing such as CVD, or the like. In addition, some semiconductor wafer susceptors have electrodes embedded in the base materials and function as electrostatic chucks configured to chuck and hold semiconductor wafers in the process of wafer transfer, an exposure, a film forming such as CVD and sputtering, a micro-processing, a cleansing, an etching, a dicing, and the like.
In these apparatuses, an electrode embedded in the ceramic base material such as aluminum nitride needs to be electrically connected to a connecting member. The portion connecting the electrode and the connecting member is subjected to heat cycles of extremely high and low temperatures in an oxidizing atmosphere and further in a corrosive gas atmosphere. Even in such severe conditions, the portion connecting the electrode and the connecting member is required to maintain a high bonding strength and a suitable electrical connection for a long period of time.
In order to solve these problems, some techniques have been proposed (see Japanese Patent Publication No. 3790000, for example). Nevertheless, problems remain yet to be solved in these proposed techniques.
For example, when an electrode connecting part is produced for a semiconductor wafer susceptor as a semiconductor device manufacturing apparatus, a connecting member and a terminal embedded in a ceramic member are bonded together with a brazed bond layer interposed in between. In general, an Au (gold)-Ni (nickel) solder Alloy is used for the brazed bond layer. However, there has been a problem in which the bonded portion is vulnerable and tends to break, after the connecting member and the terminal are bonded via the brazed bond layer. In order to solve this problem, a thicker brazing material layer (whose thickness is stably 200 μm or more) is used, or a chromium (Cr) film is provided to prevent diffusion of Ni. However, the problems have not been solved completely.
Further, a screw hole is provided in the connecting member, and a power supplying member for supplying the power to the connecting member is screwed into the screw hole. The connecting member and the power supplying member is thus connected to each other. Thus, when torque is applied more than necessary on the power supplying member, a load is applied on the connecting portion that connects the connecting member and the terminal embedded in the ceramic member, thereby the connecting portion tends to break.
Further, when the ceramic member is to be fixedly bonded with another part that contacts the ceramic member, some conventional apparatuses include a seating hole in the ceramic member, and a molybdenum metal member provided with a female screw is subjected to an aluminum (Al) brazing. However, since the melting point of brazed Al is low, the boding strength decreases at a temperature of 400° C. or higher. Thus, such a bonding structure cannot be used at high temperatures.
Accordingly, a reliable bonding structure for bonding the connecting member and the terminal embedded in the ceramic member, a semiconductor device manufacturing apparatus including this bonding structure, and a semiconductor wafer susceptor including this bonding structure have been awaited.